Aside from there being something just fundamentally messed-up about this, it seems like since all the superbanks were more or less forced to participate in TARP to mask which were in the really deep doo-doo, this is attacking an entire level of the money chain so it will inevitably be passed on to customers since there is no competitor at that level who wouldn't be affected, hence no economic check-and-balance which would prevent passing the cost down in some form. Therefore, there's nothing to keep the additional charges from just being levied on the customer base, which effectively increases the cost of borrowing and other financial transactions.
I can understand the Populist appeal of it, after all the joyride of risk without consequences at the level we're looking at is what brought the whole system to the brink of disaster. Of course the same is true of Freddie Mac and Fannie Mae, as well as AIG, GM, and Chrysler, who benefitted as well from that psychology but are not targeted by this tax/fee. I expect this law or something similar will pass just on its appeal to the short-range thinkers, and then be an anchor on commercial credit from the day it passes until it's repealed (If ever).
